Problem: 6 glue sticks cost $6.06. Which equation would help determine the cost of 7 glue sticks?
Explanation: There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 6 glue sticks cost $6.06 as a proportion: $\dfrac{6}{\$6.06}$ Let $x$ represent the unknown cost of 7 glue sticks. Since 7 glue sticks cost $x$ , we have the following proportion: $\dfrac{7}{x}$ The cost changes along with the number of glue sticks purchased, and so the two proportions are equivalent. $\dfrac{6}{\$6.06} = \dfrac{7}{x}$